O-rings are used in various applications in order to seal fluid volumes in mechanical parts against the movement of air and/or liquid. It has been found that O-rings can develop internal cracks, often referred to internal knit lines, during manufacturing. If an O-ring including an internal crack is not detected prior to the use of the O-ring, the crack may propagate to the O-ring surface, causing the O-ring to fail and allowing leakage. Depending on the application of the O-ring, the leakage can lead to failure of mechanical parts or undermine performance of a fluid handling device. For instance, certain fuel injectors, referred to as heavy fuel injectors, include passages through which coolant passes in order to cool the injectors. If a crack within an O-ring of the fuel injector propagates to the surface, the coolant can leak from the coolant passages within the fuel injector into fuel passages and eventually into a combustion chamber of an engine, causing engine performance problems.
In order to prevent problems caused by failing O-rings, O-rings used in critical applications are often inspected prior to use. Traditionally, O-rings have been visually inspected. Although defects on an outer surface of the O-ring can be visually detected, in order to determine whether there is an internal defect within the O-ring, the O-ring must often be cut open for inspection. Thus, in order to visual inspect an O-ring for internal cracks that can propagate during use of the O-ring, the O-ring must be destroyed. While such a strategy can be useful in statistically detecting O-rings with potential flaws out of a group of O-rings, defective O-rings will inevitably make their way into production fuel injectors. In addition, visual inspection is rather time-consuming because a lot of sectioning required to detect cracks over the entire perimeter of the O-ring.
The present disclosure is directed at overcoming one or more of the problems set forth above.